Three and a half billion years of life on earth
by Liz Percak-Dennett
Five members of the Wisconsin Astrobiology Research Consortium (WARC) spent the better part of September on a field trip to the Pilbara Craton, Fortescue and Hamersley Basins in Western Australia. Graduate students Liz Percak-Dennett and Jason Huberty, postdoctoral researcher Andy Czaja (who were all named Lewis and Clark Field Scholars in Astrobiology by the American Philosophical Society), and professors Clark Johnson and John Valley participated in an eight-day field trip in Western Australia led by Martin Van Kranendonk of the Geological Survey of Western Australia.
The excursion followed presentations from WARC researchers at the 5th International Archean Symposium in Perth, which was also attended by Professor Huifang Xu.
Immediately after the conference, we loaded into a 4WD off-road bus with 20 other geoscientists and drove up the sun-drenched coastline of Western Australia. By the first night the bustling cityscape of Perth had faded and we arrived on the shore of the Indian Ocean, where turquoise waters and coquina abound. We learned how to set up our swags from our van driver and local Aussie expert “Freckle”. The next day brought a once-in-a-lifetime opportunity to snorkel with stromatolites in the high-salinity waters of Shark Bay where we all got an up close look at these modern day relatives of ancient microbial communities which only exist in a few places today.
As the trip progressed, so did the journey back through geologic time. Although the first day was spent with stromatolites and modern microbial mats, these “living fossils” were quickly replaced by true fossils, and the following days allowed careful investigation of Precambrian stromatolites, highlights of which included those from the 1.8 Ga Duck Creek Dolomite, the famous Trendall locality of the 3.35 Ga Strelley Pool Formation, and the 3.48 Ga Dresser Formation at North Pole Dome.
We were also able to visit Marble Bar, the hottest city in Western Australia with a record 38 consecutive days over 100°F. Thankfully it was the cool season as we trekked across the brilliantly red, white and bluish grey banded Marble Bar cherts, as part of a several kilometer hike to witness firsthand the famous Schopf microfossil locality, home to the oldest known putative microfossils imbedded in the 3.46 billion-year-old Apex chert.
Aside from cherts and stromatolites, another key focus during the trip were the banded iron formations (BIFs). WARC researchers have been investigating BIFs for the possible role of biologic processes in forming these laminated sedimentary rocks.
We saw many of the numerous and well-preserved Archean BIFs for which Western Australia is renowned including those of the Duck Creek Dolomite (1.8 Ga), and the famous Dales Gorge Member of the Brockman Iron Formation (2.46 to 2.5 Ga) in Karijini National Park, where even a soggy walk to Circular Pool thanks to a spring shower couldn’t quell our excitement. Freckle, after attempting to assume control over 26 stubborn geologists trying to set up a tarp in the rain for our camp kitchen, later remarked that if he knew how crazy we geologists were, he would have hired a film crew and had the most popular reality TV show in Australia.
In addition to getting a chance to visit and see some of the most outstanding Archean rocks in the world, the team also got a chance to soak up some local culture, returning to North America with a newfound respect for Australian culinary delicacies, several first-hand accounts of Australian animal sightings, and some linguistic lessons straight from the Australian outback.
Originally published in The Outcrop for 2010, UW-Madison Department of Geoscience, p. 16.